Permanent form panel, assembly of said panels, and method for producing a concrete floor slab

ABSTRACT

A permanent form panel ( 1 ) for making a concrete compression slab in elevation forming a floor, said panel constituting, once the slab has been cast, the bottom portion of said slab, the panel being characterized in that it presents an “adhesion” top face having a rough surface and/or recessed or projecting means for attachment to the slab, a bottom face ( 6 ) forming a facing ready to be painted, and on at least one of its edge faces, connection means for connection to an adjacent panel in the form of means for mutual engagement and/or of a recess housing connection elements. 
     An assembly of panels with connectors arranged between the edge faces of two adjacent panels, and a method of making floor-forming concrete slabs using said panels either on site or prefabricating them.

TECHNICAL FIELD

The present invention relates to the field of fabricating shuttering floor slabs or compression slabs (topping) out of concrete cast in situ by using form panels. More particularly, the invention relates to panels for making such slabs, to assembling such panels, and to the method of making such slabs out of concrete.

PRIOR ART

Two main techniques are used at present for fabricating concrete compression slabs.

In the first technique, the method of fabricating compression slabs out of concrete that is cast in situ with its underface being used as a visible finishing medium for ceiling involves using a prop system made up of props and joists connecting the props together. Form plates are then placed on the joists and are provided with a top face that is smooth and oiled, referred to as the “forming” face, enabling the plates to be removed from beneath after the concrete has set.

That method leads to numerous defects that disturb progress on building sites and that lead to fabrication defects. Stripping the plates presents a safety risk for workers since they can drop unexpectedly. Taking down reusable form plates requires a manually operated mechanical device that is bulky and difficult to move between the floors of a building. That method leads to a large amount of manual handling in order to take the plates away from an area after stripping.

Furthermore, imperfect junctions between those shuttering plates lead to defects in the ceilings that subsequently require lengthy operations of sanding and smoothing surfaces by hand.

Furthermore, the rough surface state of the raw concrete is not suitable for being painted directly, so it is necessary to apply at least two layers of the smoothing coating before applying paint.

Reusable form plates are generally panels of plywood or of polymer materials that become progressively degraded and deformed as they are used and reused, thereby degrading the finishing quality of ceilings as a building site advances. This results in lengthening the duration of smoothing and sanding work on the ceilings prior to applying the coating followed by paint.

In the second technique, the usual method consists in putting shuttering floor slabs into place, i.e. plates of concrete that are prefabricated in a factory or in temporary pre-fabrication plants. Once positioned on the formwork of the floor, the shuttering floor slabs act as bottom forms for casting an additional thickness of concrete that co-operates with the shuttering floor slabs. That method makes it possible to use a prop system that is simplified since the shuttering floor slabs have their own structural strength and incorporate some of the reinforcing bars of the compression slab.

The major drawback found with the shuttering floor slab system lies in processing the joints in their bottom face. Joints are processed with a suitable coating, but surface cracks inevitably appear between the shuttering floor slabs as a result of the concrete shrinking. These slabs are also heavy and expensive to transport. They require large storage areas on site.

Finally, putting arrays into place in a floor slab is made more complex since the volume of concrete that is cast in place is less than when making a compression slab that is entirely cast in place.

The bottom faces of the shuttering floor slabs are made of raw concrete and cannot be painted directly for the reasons mentioned above, so it is essential to apply a coating before applying paint.

DESCRIPTION OF THE INVENTION

A first object of the invention is to remedy the problems of safety, of ergonomics, and of finishing quality while making floor-forming compression slabs in the field of building.

Another object of the invention is to propose form panels that enable such floor-forming concrete compression slabs to be made.

To this end, the present invention provides a permanent form panel for making a concrete compression slab forming a floor, said panel constituting, once the slab has been cast, the bottom portion of said slab, the panel being characterized in that it presents:

-   -   an “adhesion” top face having a rough surface and/or recessed or         projecting means for attachment to the slab;     -   a bottom face forming a facing; and     -   on at least one of its edge faces, connection means for         connection to an adjacent panel in the form of means for mutual         engagement and/or of a recess housing connection elements.

This permanent form panel thus co-operates with the concrete compression slab that is cast onto it throughout the lifetime of the work.

The term “slab” is used herein to cover both a slab that is made directly on a building site, and a slab that is prefabricated in a factory and transported to the building site.

The use of such a panel makes it possible to eliminate the operation of stripping the forms, together with the associated time and constraints. Furthermore, the structure of the top face of the concrete panel, once it has set, adheres to said panel, and the bottom face of said panel forms a facing and does not require a coating to be applied prior to applying paint.

Even though it remains secured to the concrete slab throughout the lifetime of the work, the form panel of the invention does not contribute to the structural strength of the concrete compression slab. That is what distinguishes it from a shuttering floor slab. After the concrete has set, the form panel of the invention remains secured to the slab and serves as a finishing covering for the underface of the slab.

The attachment means of the top face of said panel may be sockets of undercut shape, such as sockets of dovetail shape.

Casting the slab or the shuttering floor slab requires a plurality of panels of the invention to be assembled together, which panels include connection means for connecting them together. These connection means for connection to an adjacent panel may comprise means for direct engagement with said adjacent panel, such as complementary rabbets or shapes of the tongue-and-groove type. In a variant, the connection means may comprise connector type elements, as described in greater detail below in the description.

Advantageously, the bottom face of said panel includes chamfered edges or thinned edges, constituting housings for applying a jointing coating and possibly an anti-cracking strip between two adjacent panels, thereby making it possible to obtain a finish without visible joints and without extra thickness.

The bottom face of said panel, referred to as the “facing” face, advantageously presents a surface of generally plane shape and is preferably pale in color. A reflection factor greater than 70%, preferably greater to or equal to 80%, more preferably greater than or equal to 90%, is entirely appropriate for constituting the finishing face, such as a ceiling, of the slab or of the shuttering floor slab.

Preferably, the bottom face of said panel is made of a material presenting porosity and/or capillarity that also enables it to be covered by coating and/or paint.

In a first embodiment of the invention, the panel is formed by a single-piece block, preferably made of a material based on MgO, MgCl₂, and fibers. Advantageously, the fibers are flush with the surface of at least the top face of the panel in order to constitute the rough adhesion face for the concrete. This material based on MgO, MgCl₂, and fibers is sufficiently porous to enable a paint to adhere by capillarity, for example.

In a second embodiment of the invention, the panel includes a core comprising a thermally insulating material and/or imparting soundproofing properties to said panel.

For example, the core of said panel may lie between a top layer and a bottom layer, each formed by a material including fibers coated in a binder, preferably said binder of the top layer comprises an elastomer polymer, such as a latex or styrene-butadiene type polymer, and preferably the binder of the bottom layer comprises a material including magnesium oxide and magnesium chloride.

The polymer of the top layer may be an emulsion of latex polymer of ethylene vinyl acetate (EVA) type (C₄H₆O₂-C₂H₄)_(n) or of styrene-butadiene rubber (SBR) type (C₈-H₈.C₄-H₆)_(n), possibly mixed with a hydraulic binder such as Portland cement.

The above-mentioned fibers may be of any type, but they are advantageously glass fibers.

The panel of the invention is not a structural element of the slab, and its main function is to support the concrete cast on its top face. Consequently, and as mentioned above, it is of smaller thickness than a conventional shuttering floor slab. The thickness of the concrete above is sufficient to be able to embed reinforcing bars therein, and also electrical, hydraulic, or air-flow connection conduits.

Consequently, in an advantageous variant, at least the top face of the panel of the invention presents reception means for receiving elements such as boxes and/or conduits for electrical and/or hydraulic connections, said elements preferably being suitable for being releasably mounted on said top face of the panel. These said reception means may advantageous be arranged projecting from said top face, such as collars of cable clamp type, collars, or self-gripping coverings, or are in the form of grooves formed in the top portion of said panel.

In another variant of the invention, at least one of the faces of said panel may have markers and/or lines suitable for positioning it as formwork on site and for guiding the positioning of auxiliary elements:

-   -   on the top face, elements for incorporating in the concrete that         is to be cast on said panel, such as reinforcement for the         concrete, electrical, hydraulic, and/or air-flow boxes and/or         conduits, locations for doors and windows, thermal barriers, or         balconies; and/or     -   on the bottom face for guiding the positioning of partitions,         soffits for the underlying floor, and/or elements that are to be         fastened to said ceiling-forming panel.

In a preferred embodiment, the panel of the invention includes simultaneously reception means for elements such as boxes and ducts for electrical, hydraulic, and/or air-flow connections, reinforcing bars for concrete, thermal barriers, and positioning markers and/or lines on one of its top and bottom faces.

At least one of the faces of said panel may be provided with cutouts for fitting the dimensions of said panel to the limits of the area to be covered in formwork and/or for forming through orifices. Such through orifices may for example constitute reserved passages (from one floor to another) or serve to receive through conduits or pipes.

The present invention also provides an assembly of permanent form panels for making in an elevated floor-forming concrete compression slab, the assembly comprising panels as described above.

In a preferred embodiment of the invention, said assembly may include connectors positioned in recesses formed between two adjacent panels, each connector comprising a foot of conical shape fitting in a housing of upside-down V-shape that is formed between said adjacent panels, and surmounted by a rod terminated by a head bearing against the top faces of two adjacent panels. The head of said connector may also be conical or rounded in shape to enable panels assembled with connectors to be stacked for storage or transport purposes.

The present invention also provides a method of making an elevated concrete compression slab or for prefabricating concrete compression slabs.

The method of making an elevated floor-forming concrete compression slab, advantageously comprises the following successive steps:

-   -   making form panels as described above:     -   assembling and propping said panels in compliance with a         predefined plan and with numerical and visible markers for         positioning them (in the correct orientation);     -   laying reinforcing bars, conduits, and/or cabling, laying boxes         or shuttering, and putting partitions into place in compliance         with lines made on at least one of the faces of said panels         and/or with the help of reception means provided in at least one         of the faces of said panels; and     -   casting concrete on the top faces of said panels.

The method of prefabricating floor-forming concrete slabs advantageously comprises the following successive steps:

-   -   making form panels as described above;     -   assembling said panels on the prefabrication bench in compliance         with a predefined plan and with numerical and visible markers         for positioning them;     -   laying reinforcing bars, conduits, and/or cabling, making         reservations, and putting partitions into place in compliance         with lines made on at least one of the faces of said panels         and/or with the help of reception means provided in at least one         of the faces of said panels; and     -   casting concrete on the top faces of said panels.

Finally, the present invention also provides any assembly comprising a concrete slab and at least one panel as described above, made in accordance with one of the above methods.

BRIEF DESCRIPTION OF THE FIGURES

The invention can be well understood on reading the following description of embodiments given with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view from above of form panels of the present invention in use on a prop device;

FIG. 2 is a perspective view from above of a panel of the invention;

FIG. 3 is a perspective view from beneath of a panel of the invention;

FIG. 4 is a fragmentary section view of an end of a panel provided with a tongue;

FIG. 5 is a fragmentary section view of two adjacent panels having tongue-and-groove type edges;

FIG. 6 is a fragmentary section view of two adjacent panels having edges with complementary rabbets;

FIG. 7 is a fragmentary perspective view of a panel showing a first edge including a tongue and a different second edge having a lateral recess for such a tongue;

FIG. 8 is a fragmentary section view of two adjacent panels having chamfered bottom edges;

FIG. 9 is a fragmentary section view of two adjacent panels having thinned bottom edges;

FIG. 10 is a perspective view from beneath of a panel having chamfered bottom edges and including recesses for connectors;

FIG. 11 is a perspective view from beneath of a panel having thinned bottom edges including recesses for connectors;

FIG. 12 is a side view of a connector;

FIG. 13 is a fragmentary perspective view from above of an assembly comprising two adjacent panels and a connector;

FIG. 14 is a fragmentary section view of two superposed panels with connectors;

FIG. 15 is a section view of a panel including a core made of material having soundproofing properties;

FIG. 16 is a plan view of an assembly of a plurality of panels of the invention fitted with electrical conduits;

FIG. 17 is a fragmentary perspective view from above showing a detail of an electrical connection provided on the top face of a panel of the invention;

FIG. 18 is a fragmentary perspective view from above showing details of reception means for receiving electric cables arranged on the top face of a panel of the invention; and

FIG. 19 is a plan view showing various markers and lines on the top face of an assembly of panels of the invention.

DETAILED DESCRIPTION

With reference to the figures, the panel 1 of the invention is a form panel of rectangular shape having mechanical characteristics that are designed to withstand a point load such as a person walking on the form prior to casting concrete, and to withstand thrust from the concrete while it is being cast.

The bending strength of the panel depends on the span between structural joists 3 supported by vertical props 2 of the prop device provided in the context of its use. This bending strength is adjusted by modulating the thickness of the form panel as a function of the prop system used. The amount of sag that is acceptable between joists 3 is calculated as a function of the acceptable tolerances for a finished ceiling in the field of building.

The material constituting the form panel 1 advantageously presents a high degree of dimensional stability, and in particular maximum expansion or shrinkage that is preferably 0.2% when it is subjected to the maximum variations in humidity and temperature that are observed in the area where the device is used. In particular, the material presents maximum expansion or shrinkage of 0.2% when covered with concrete in the liquid state.

In the presently-described example, the material constituting the form panel of the invention is a composite material constituted by a mineral body 5 formed by agglomerating magnesium oxide (MgO, 30% to 60%), magnesium chloride (MgCl₂, 20% to 50%), and perlite (Fe₃C, 3% to 15%).

The top and bottom faces 4 and 6 (see FIG. 4) comprise respective layers of woven or non-woven glass fibers. These two glass fiber layers are inlaid in the matrix of the body of the panel.

The face referred to as the “bottom” face 6 (FIG. 3) of the form panel 1 is the face that is located underneath when the panel is put into place on the joists 3 of the prop device. It is this surface that becomes visible on the underside of the concrete slab when the prop device is removed.

The form panel of the invention is characterized by a bottom face 6 that is sound, smooth, and regular, satisfying in particular the adhesion capacity requirements for all types of water-based paints used for main surfaces in residential buildings. The surface presents porosity and capillarity that are appropriate for bonding with such paint.

The above-mentioned mineral composite material satisfies these constraints of paint adhesion and regularity for the bottom face 6. A bottom face 6 of the form panel made using this composite material presents water absorption capacity lying in the range 5% to 30%, preferably close to 20%, and a pale color (reflection factor of the surface being at least 70%) enabling it to be painted with two coats of color.

On its four edge faces, the permanent form panel 1 of the invention presents means for connection with adjacent panels, serving to ensure continuity between a plurality of panels of identical design assembled in abutment. The connection means serve in particular to ensure that together the panels 1 are plane so as to satisfy the planeness requirements of media ready for painting and they serve to provide leaktightness so that concrete cannot pass between the panels 1.

By way of example, the connection means make the following assemblies possible:

-   -   Assembly of the “tongue-and-groove” type (FIG. 5). The panel         then has tongue-type projecting portions 8 on two contiguous         edge faces and complementary portions of groove type 9 set back         in the other two edge faces. These tongue-and-groove connections         are designed to engage mutually when a plurality of panels         (FIG. 1) are placed side by side to form a set that can be         extended to infinity (FIG. 1). The mutual engagement (FIG. 5)         serves to guarantee that the panels 1 are accurately fitted and         flush relative to one another and to compensate for potential         defects in the adjustment of the prop device. Such an assembly         makes it possible to ensure hermetic jointing between the panels         so as to prevent concrete from flowing between the panels.     -   Assembly of the “tenon-and-mortise” or “lug” type (FIGS. 4 and         7). The panel then has tenons or lugs 12 distributed at regular         intervals on two contiguous edge faces, and recesses 13 of         complementary shape formed in edge faces and situated at exactly         the same intervals in the other two edge faces. These appendices         are designed to engage mutually when a plurality of panels 1 are         joined side by side to form a set that can be extended to         infinity (FIG. 1). The assembly is not so leaktight as the above         assembly between the panels 1 when concrete is cast. A chamfered         top edge 15 is then provided at all of the edges of the top face         (FIG. 8). These chamfered edge 15 provide recesses for applying         a joint of elastomer sealant after the panels have assembled         together on the site where the formwork is being made.     -   Assembly of the “overlap” type (FIG. 6). The panel 1 then         presents edges with complementary rabbets 10 and 11 that are         formed respectively level with the top face for two contiguous         edges (e.g. the rabbet 11) and level with the bottom face for         the other two edges (e.g.

the rabbet 10). When a plurality of form panels are assembled together (as shown in FIG. 1), these shapes enable one rabbet to overlie another rabbet of opposite shape. The engagement serves to guarantee that mutually adjacent panels are accurately fitted and flush, and to compensate for any defects in adjusting the prop device. This assembly provides hermetic jointing between the panels and thus prevents concrete flowing between the panels.

-   -   Assembly by means of “connectors” 18 (see FIGS. 12, 13, 14) that         are distributed over two contiguous edges of each of the panels         that are to be assembled together. In the example shown in FIGS.         12 and 13, each connector 18 comprises a foot 19 of conical         shape that fits in a housing having an upside-down V-shape that         is formed between the bottom edges of adjacent panels. The foot         19 is surmounted by a rod 20 that is received in recesses 17         (see FIGS. 10 and 11) formed in the edge faces of the panels,         and it terminates in a head 21 that bears against the top faces         4 of two adjacent panels.

The recesses 17 formed in the edge faces of the panels serve to define accurate positioning for the connectors 18 and holds them by the connectors being engaged in predefined positions relative to said panels. These recesses 17 in the edge faces enable the panels 1 to be fitted against each other without any gap, thus ensuring maximum leaktightness when casting fresh concrete (see FIG. 13).

Where appropriate, the edge faces of a said panel that do not have connectors nevertheless present recesses of shape designed to match the shape of connectors fastened to another panel that is identical when the two panels are positioned side by side, whether this is in the width direction or the length direction, with the two assembled-together panels always being oriented in the same direction. These recesses may then also act as keying means when assembling panels together on site.

The shape of the connectors 18 is designed to enable the panels to be stacked during storage: the base of the foot 19 is hollowed out so as to receive the conical or rounded head 21 of said connector, thereby enabling panels assembled with connectors to be stacked.

The top face 4 (see FIG. 2) of the permanent form panel 1 of the invention presents means for bonding with the concrete of the slab once it has set.

Bonding with concrete may be achieved in several ways:

One or more blind recesses 7 (shown diagrammatically in FIGS. 2, 4, 8, and 9) are cut out in the top face 4 of the permanent form panel 1. The recess(es) have an undercut shape so as to prevent a liquid body that has set from being extracted therefrom. The shape may be a dovetail shape with a trapezoidal profile (as shown diagrammatically in FIGS. 2, 4, 8, and 9) with its large base being situated at the bottom of the recess, or it may be any other profile that becomes larger than its size measured at the surface of the panel. These means for bonding by recesses with an undercut shape constitute non-releasable connection means between the panel and the concrete cast in place on its top face (FIG. 2), which concrete becomes trapped in these recesses once it has set. The recesses are preferably uniformly distributed over the top surface 4 (FIG. 2) in order to ensure that load is spread over the entire surface of the permanent form panel 1.

-   -   One or more appendices are fastened on the top face (FIG. 2) of         the permanent form panel and project from the surface of the         panel. The shape of the appendix(ices) then necessarily presents         an undercut ensuring that it/they cannot be separated from the         concrete after it has been cast on the top surface 4 of the form         panel and has set. The appendix(ices) may be assembled with the         form panel by adhesive, by mechanical fastening, or by         interfitting complementary shapes. This type of assembly is         preferred when the thickness of the panel is too small to form         recesses in the material of the body of the panel. The bonding         appendix(ices) may also serve as spacers for laying an optional         sheet of metal reinforcement on the form to be covered when         casting the concrete so as to form reinforced concrete. The         appendix then serves to maintain a distance of a few centimeters         (e.g. 2 cm to 5 cm) for the concrete coating between the         permanent form panel and the sheet of reinforcement.

When the finish desired for the smooth ceiling is not to leave interstices visible between adjacent panels 1, a jointing system is then provided that is partially incorporated in the panel.

By way of example, the jointing may be performed in two ways:

-   -   The four edges of the permanent form panel may be thinned edges         16, in the bottom face 6 only (FIG. 3), e.g. having a depth of         one to three millimeters and a width of no more than sixty         millimeters. Abutting the thinned edges 16 of two adjacent form         panels leaves a recess in which an anti-cracking strip can         subsequently be laid with adhesive and coated in a plurality of         passes with a coating appropriate for the support material         without generating extra thickness that can be seen by the naked         eye. The strip is adhesively bonded in the recess created by the         thinned edges 16 (see FIG. 9) in each of two assembled-together         adjacent panels.     -   The four edges of the permanent form panel may be chamfered         edges 14 of its bottom face 4 (FIG. 8). The chamfer presents an         open angle, preferably of more than 45°, so as to provide a         maximum attachment area for the coating used for stopping.

The recess formed by abutting chamfered edges 14 of two adjacent panels enables a special purpose stopping coating to be applied subsequently. After the stopping coating has dried, it is possible to apply a finishing coating to permanently mask the junction between the two panels.

The permanent form panel 1 of the invention may be placed as the bottom of the formwork on the base plate of industrial or temporary pre-casting plants. After the formwork has been removed from the floor slab, the form panels co-operate with the slab in permanent and irreversible manner. They thus serve as a permanent finishing covering of the underface of the prefabricated slab. This provision makes it possible to paint the underface of the prefabricated slab directly without any prior step of preparing the medium.

In the example shown in FIG. 15, the panel 1 has a core 22 co-operating with thermally insulating material and/or providing said panel with soundproofing properties, which material is interposed between a top layer 24 at the rough top face 4 and a bottom layer 26 at the bottom face 6, which is ready for painting.

Each of the top and bottom layers 24 and 26 may be formed by a material including fibers, such as glass fibers coated in a binder. The binder of the top layer 24 may comprise an elastomer polymer, such as a polymer of the latex or styrene-butadiene type, possibly mixed with cement, such as Portland cement. The binder of the bottom layer 26 may be a material including magnesium oxide and magnesium chloride.

The core 22 may be made of a high resilience material having a sound absorption coefficient a_(w) of more than 0.10 (in compliance with the ISO 11654 standard) for sound frequencies in the range 0 to 40,000 hertz (Hz). After the slab has been cast, and after the prop device has been dismantled, said resilient core lies between two rigid walls referred to as “masses”: the top mass is constituted by concrete which generally has a specific gravity of 2.4 to 2.8, while the bottom mass is the bottom layer 26 of the form panel 1 which has a specific gravity greater than 1.

The assembly as created in this way constitutes a mass/spring/mass system that improves the sound performance of the assembly comprising the slab plus the panels, in particular for the category of air-borne noise and for the category of noise from impacts against the floor on the top surface of the slab, and indeed against the ceiling of its bottom surface.

In order to further facilitate work on the building site, the panels 1 may advantageously be provided on their top faces 4 and/or on their bottom faces 6 with means for receiving elements such as boxes 30 or conduits 31 for electrical, hydraulic, and/or air-flow connections, said elements preferably being suitable for being removably mounted on said top face 4 of the panel.

For example, as shown in FIGS. 16, 17, and 18, these panels may be pre-fitted with reception means arranged projecting from said top face 4, such as cable-clamp type collars 25, collars, or self-adhesive covering type, e.g. in the form of self-adhesive pads stuck onto the surface: the bases of the boxes 30 likewise present self-gripping zones and can thus be put into place quickly, accurately, and releasably.

Said reception means may also be in the form of groves formed in the top portion of said panel.

This pre-outfitting of the panels 1 thus enables housing boxes 30 and connection conduits 31 to be positioned accurately and quickly since there is no need to read a drawing and make use of manual measurement means (tape measure); this positioning of shuttering boxes on the panels 1 nevertheless remains flexible since, where necessary, they can be shifted by a few millimeters in order to avoid the reinforcing bars of the concrete. The boxes 30 can also be removed easily and put back into place.

Furthermore, at least one of the faces of said panel may be provided with markers 27 and/or lines 28, 29 (see FIG. 19) suitable for positioning it as a piece of formwork on site and for guiding the positioning of auxiliary elements:

-   -   on the top face 4, elements that are to be incorporated in the         concrete that is to be cast on said panel, such as reinforcement         for the concrete, electricity, hydraulic, and/or air flow         networks, locations for doors and windows, thermal barriers, or         balconies; and/or     -   on the bottom face in order to guide the positioning of         partitions (lines 28 in FIG. 19), soffits of an underlying         floor, and/or elements for fastening to said ceiling-forming         panel.

Thus, each plate is identified by a number 27 that corresponds to the order of laying and that relates to a plan. The lines 28 correspond to the real locations in three dimensions and at life size for the reinforcing bars, networks, and boxes 30 that need to be incorporated in the concrete slab and that need to be put into place before casting. All of these markers and lines serve as guides for operators while positioning the equipment that is to be incorporated in the slab.

The assembly of the form plates then forms a kind of jigsaw puzzle (FIG. 19) where all of the information useful for construction of the building appears in the form of a plan at life size on the building. The operator therefore has no need to refer to plans on paper, nor to make use of measurement tools for positioning the various elements. Measurements and positioning errors are then considerably reduced, or even eliminated. This likewise results in a huge saving in time on the building site. 

1. A permanent form panel for making a concrete compression slab forming a floor, said panel being, once the slab has been cast, the bottom portion of said slab, the panel comprising: an adhesion top face having a rough surface and/or recessed or projecting means for attachment to the slab; a bottom face forming a facing; and on at least one of its edge faces, connection means for connection to an adjacent panel in the form of means for mutual engagement and/or of a recess housing connection elements.
 2. A panel according to claim 1, wherein the attachment means of the top face of said panel are sockets of undercut shape, such as sockets of dovetail shape.
 3. A panel according to claim 1, wherein the means for connecting to an adjacent panel comprise means for direct engagement with said adjacent panel, such as complementary rabbets or shapes of the tongue and groove type.
 4. A panel according to claim 1, wherein the connection means comprise connector type elements.
 5. A panel according to claim 1, wherein the bottom face of said panel includes chamfered edges or thinned edges, that are housings for applying a jointing coating and possibly an anti-cracking strip between two adjacent panels.
 6. A panel according to claim 1, wherein the bottom face of said panel, referred to as the “facing” face, presents a surface of generally plane shape and is preferably pale in color.
 7. A panel according to claim 1, wherein the bottom face of said panel is made of a material presenting porosity and/or capillarity that enable it to be covered by coating and/or paint.
 8. A panel according to claim 1, wherein said panel is constituted by a single-piece block, preferably made of a material based on MgO, MgCl₂, and fibers.
 9. A panel according to claim 1, wherein said panel includes a core comprising a thermally insulating material and/or imparting soundproofing properties to said panel.
 10. A panel according to claim 9, wherein the core lies between a top layer and a bottom layer each formed by a material including fibers coated in a binder, preferably said binder of the top layer comprises an elastomer polymer, such as a latex or styrene-butadiene type polymer, and preferably the binder of the bottom layer comprises a material including magnesium oxide and magnesium chloride.
 11. A panel according to claim 1, wherein at least the top face (4) of said panel presents reception means for receiving elements such as boxes and/or conduits for electrical and/or hydraulic connections, said elements preferably being suitable for being releasably mounted on said top face of the panel.
 12. A panel according to claim 11, wherein the reception means are arranged projecting from said top face, such as collars of cable clamp type, collars, or self-gripping coverings, or are in the form of grooves formed in the top portion of said panel.
 13. A panel according to claim 1, wherein at least one of the faces of said panel has markers and/or lines suitable for positioning it as formwork on site and for guiding the positioning of auxiliary elements: on the top face, elements for incorporating in the concrete that is to be cast on said panel, such as reinforcement for the concrete, electrical, hydraulic, and/or air-flow boxes and/or conduits, locations for doors and windows, thermal barriers, or balconies; and/or on the bottom face for guiding the positioning of partitions, soffits for the underlying floor, and/or elements that are to be fastened to said ceiling-forming panel.
 14. A panel according to claim 1, wherein at least one of the faces of said panel is provided with cutouts for fitting the dimensions of said panel to the limits of the area to be covered in formwork and/or for forming through orifices.
 15. An assembly of permanent form panels for making in an elevated floor-forming concrete compression slab, the assembly comprising panels according to claim
 1. 16. An assembly of panels according to claim 15, wherein said assembly of panels it includes connectors positioned in recesses formed between two adjacent panels, each connector comprising a foot of conical shape fitting in a housing of upside-down V-shape that is formed between said adjacent panels, and surmounted by a rod terminated by a head bearing against the top faces of two adjacent panels.
 17. A method of making an elevated floor-forming concrete compression slab, the method comprising the following successive steps: making form panels according to claim 1; assembling and propping said panels in compliance with a predefined plan and with numerical and visible markers for positioning them; laying reinforcing bars, conduits and/or cabling, laying boxes or shuttering, and putting partitions into place in compliance with lines made on at least one of the faces of said panels and/or with the help of reception means provided in at least one of the faces of said panels; and casting concrete on the top faces of said panels.
 18. A method of prefabricating floor-forming concrete slabs comprising the following successive steps: making form panels according to claim 1; assembling said panels on the prefabrication bench in compliance with a predefined plan and with numerical and visible markers for positioning them; laying reinforcing bars, conduits, and/or cabling, making reservations, and putting partitions into place in compliance with lines made on at least one of the faces of said panels and/or with the help of reception means provided in at least one of the faces of said panels; and casting concrete on the top faces of said panels.
 19. (canceled) 